Three nestlings born in recent weeks to red-tailed hawks in the south end of Riverside Park in Manhattan are believed to have died, bird experts said on Monday. The body of only one young hawk — or eyas — has been recovered so far. The city’s avid bird-watchers have confirmed that the other two babies are not in their West Side nest and are feared dead as well.... “On Sunday morning I went out at 7 a.m.,” Dr. [Leslie] Day said in a phone interview on Monday. “Standing at the nest, I could see there were no babies. They had become so large, standing at the rim, strengthening their wings.” ... While the cause of death awaits a toxicology analysis, Dr. Day suspected that the parents may have fed the nestlings pigeons or rats that contained lethal levels of poison — a common cause of death for the delicate hawks.In his website palemale.com, where the photo above appears, photographer Lincoln Karim later wrote, "UC Davis lab results are in for the 1st retrieved baby hawk from Riverside Park: Blood/organ samples contained lethal levels of two anti-coagulant rodenticides.... All poisoning of animals must stop now! Starting with Riverside Park and Central Park."